IMA001 Is a Novel Therapeutic Molecule That Reduces Sickling and Hemolytic Anemia Markers in a Sickle Cell Disease Mouse Model

Introduction:

Sickle Cell Disease (SCD) is an autosomal recessive monogenic disorder affecting the β-globin gene and leading to red blood cell (RBC) sickling, hemolytic anemia, vaso-occlusion, inflammation and end-organ damage. Although SCD is well described at the molecular level, there are still unmet needs for disease modifying treatments. We have identified IMA001, a nucleotide involved in coenzyme mechanisms central to cellular metabolism, which shows efficacy in improving anemia- and hemolysis-related markers with a favorable safety profile.

Experimental design:

IMA001 (185 mg/kg/day; n=5 to 7) or vehicle (phosphate-buffered saline; n=5 to 6) were injected intra-peritoneally in 3 independent cohorts of the Townes HbSS mice once daily for: 14 days in cohort 1, 28 days in cohort 2 and 3. Blood was collected on day 0, 5, 10 and 15 for cohort 1, on day 29 for cohort 2 and on day 21, 22, 24, 27 and 29 for cohort 3. Blood was used to perform RBC ex-vivo sickling assay in hypoxic environment (1% O₂ for 1 hour) and fetal hemoglobin (HbF) analysis by flow cytometry (cohort 1 and 2), routine hematology counts (all cohorts). In addition, spleens were collected and weighed (cohort 1 and 2). To assess RBC half-life, the percentage of circulating biotinylated RBCs were monitored by flow cytometry at day 0, 1, 3, 6 and 8 following biotin administration (at day 21 of IMA001 treatment in cohort 3).

Results:

RBC sickling - RBCs from mice dosed with IMA001 for up to 15 days (cohort 1) showed significant reduction of sickling at all time points in comparison to baseline (-72% at day 5, p<0.01; -76% at day 10, p<0.01 and -84% at day 15, p<0.01). Consistently, cohort 2 showed a markedly reduced sickling in IMA001-treated vs. vehicle-treated groups (-56%, p<0.01).

Anemia and hemolysis markers - IMA001 treatment in cohort 2 mice resulted in significant increase in hemoglobin levels (+1,31 g/dL vs. vehicle, p<0.001) and RBC counts (+23% vs. vehicle, p<0.001). Accordingly, this was associated with a 25% increase in hematocrit in the IMA001-treated vs. vehicle-treated groups (p<0.001) and with marked reduction in spleen weights (-17% in the mean spleen to body weight ratio, p<0.001). Additionally, IMA001 treatment for 14 and 28 days, reduced the number of circulating reticulocytes. In cohort 1, reduction of 22% and 60% was observed at day 10 and 15 respectively (p<0.001 at both time points) when compared to day 0. In cohort 2, IMA001 also decreased reticulocytes count by 21% (p<0.001).

Fetal hemoglobin expression in RBCs - In cohort 1, significant 2-fold increase in F-cell percentage was observed in IMA001-treated mice at 15 days vs. day 0 (p<0.01). These data were confirmed in cohort 2 IMA001-treated mice that also showed increased HbF cellular content reflected by an increase of 29% in HbF mean fluorescence intensity in comparison to the vehicle-treated group (p<0.01).

RBC half-life - In mice from cohort 3 administered with IMA001, RBC half-life was improved (3.95 days vs. 2.38 days in the vehicle group). Specifically, higher percentages of biotinylated RBCs were found at days 3 and 6 (+74% and +174% in IMA001-treated vs. vehicle-treated groups respectively, p<0.01 at both time points).

Conclusion:

Our study shows that IMA001 is a potent molecule that improves the critical hematological markers of SCD. This is reflected by its capacity to reduce sickling and to increase RBC half-life in the circulation leading to a significant increase in hemoglobin levels. This feature on anemia alleviation has a direct physiological effect in the Townes mice, as highlighted by the mitigation in spleen size indicating a positive impact on stress erythropoiesis. Overall, these data demonstrate the potential of IMA001 as a promising new, safe and effective treatment for SCD.